Device for monitoring the flow of a fluid flowing through or from a conduit, such as a lubricant, and the monitoring method implemented by the device

ABSTRACT

A device for monitoring the flow of a fluid ( 3, 13 ) flowing through or from a conduit ( 2 ), such as a lubricant or an article treatment fluid; it includes light-emitting elements ( 1 ) arranged to irradiate a light radiation towards the flow and sensor elements ( 4 ) for sensing the image projected onto them by the fluid ( 3, 13 ) struck by the light radiation, the sensor elements ( 4 ) generating at least one output signal ( 11, 12 ) based on the presence thereon of the sensed fluid image. The method implemented by the device is also claimed.

The present invention relates to a device for monitoring the flow of afluid flowing through or from a conduit, such as a lubricant or anarticle treatment fluid. The invention also relates to a methodimplemented by the said device.

In the present text, the term “fluid” means any element or flow which isliquid, gaseous or composed of particles or powders suspended in agaseous or liquid means which transports them.

Processes are known which require precise monitoring of the state offeed of a fluid. For example, one of these is the well known lubricationprocess; in this process extremely small or large quantities oflubricant, such as oil, are fed through connection pipes between an oilpumping member and a member to be lubricated, for example the bearingsof a machine tool spindle, or the tool of the actual machine whilemachining a workpiece. Such lubrication is evidently important because,as is obvious, any interruption therein would in the first case lead tobreakage of the bearings, and in the second case the breakage of thetool.

Other processes also exist in which a fluid, for example a paint, apowder, etc., is sprayed onto an article; in such processes, a sprayinginterruption or irregularity would result in rejection of the piecesproduced. In still further processes, such as fabric oiling with oilsand/or specific substances, said substances are applied during thewinding of a spool of yarn; again in this case, any interruption in thefeed of said substances to the yarn treatment station in which sprayingis carried out would represent a serious defect in the yarn oilingprocess.

From WO 01/36861 a method (and corresponding device) are known formonitoring the flow of the oil used with air to lubricate mechanicalcomponents. This method consists, inter alia, of using an optoelectronicsensor comprising a light source and a receiver, between which there ispositioned a transparent portion of a conduit through which oil and airpass, directed towards a member to be lubricated. The receiver isconnected to a control member which, on the basis of the light sensed bythe receiver, modifies the intensity of the radiation emitted by thelight source in order to maintain a constant light quantity striking thereceiver notwithstanding the attenuation generated on the light by thefluid passing through the conduit. This control member is also connectedto a circuit which, on the basis of the signals which cause the lightsource to modify the intensity of the emitted light, defines thequantity of oil fed to the lubricated member or the intensity of the airflow present in the said conduit, or deactivates said lubricated member(warning of any flow abnormalities through the conduit).

The aforedescribed known device therefore evaluates the fluid flow ratethrough the conduit, which however depends on continuous modificationsto the intensity of the light generated by the light source, in order tomaintain the value sensed by the receiver constant. The flow rateevaluation must therefore consider a light unit compensation time (tomaintain the value sensed by the receiver constant), and it is notpossible to achieve a flow rate evaluation within a very short time(i.e. within real time).

Moreover if the fluid passing through the conduit is not permeable tolight (such as paint), the known device is unable to determine a correctflow rate of this fluid as the light source cannot be controlled in sucha manner as to enable the receiver to receive a light signal.

The known solution does not enable measurement of a flow rate of fluidemitted (for example sprayed) by an atomizer or spray nozzle. Moreover,the known solution uses a simple optical sensor and does not enablefluid to be monitored through a conduit of large dimensions (such asthose used for example to transport the water/oil emulsion forlubricating tools in numerically controlled automatic machines).

An object of the present invention is to provide a device able tomonitor with absolute certainty the state of feed or flow interruptionof a fluid fed to an operative zone or station from a relative tank orfeed zone, such monitoring also being possible for a fluid which is notpermeable to light.

Another object is to provide a device of the stated type which in no wayinfluences the flow being monitored and which enable the state of thefluid and/or its flow rate to be directly determined, without thisdetermination being subject to time variables related to adjustmentswithin the device or in the operative modalities thereof.

Another object is to provide a device of the stated type which is ofvery small dimensions, such that the device can be easily applied in aplace or on a machine in which a fluid of the stated type is used.

A further object is to provide a device of the stated type which iscompletely programmable to enable it to be easily adapted to the mostdisparate applications.

A further object of the present invention is to offer a methodimplemented by the aforesaid device.

These and further objects which will be apparent to the expert of theart are attained by a device and method in accordance with theaccompanying claims.

The present invention will be more apparent from the accompanyingdrawing, which is provided by way of non-limiting example, and in which:

FIG. 1 is a schematic view of a first method of using the device;

FIG. 2 is a schematic view of a second method of using the device;

FIG. 3 shows a circuit schematic of one embodiment of the device of theinvention.

With reference to said figures, in FIG. 1 the reference numeral 1indicates a light transmitter consisting for example of a known diode(LED) model OP240A produced by OPTEK of the type with wavelength forexample 960 nm, a typical wavelength in the infrared region; 2 indicatesa tube or conduit for example of thermoplastic material, of the typeused for feeding oil or air/oil mixtures. Through the tube 2 there isshown a typical air/oil flow 3 of the type used for example forlubricating the bearings of a machine tool, said fluid being fed throughthe tube 2 from a source in known manner. The tube 2 is transparent tolight (in the example, to infrared light radiation) at least within thatportion facing the light transmitter 1. It should be noted that theemitted light has a suitable wavelength (for example, within theinfrared or ultraviolet range) to prevent interference with the tube 2.

The reference numeral 4 indicates a light sensitive sensor or receiverarranged to cooperate with the transmitter 1. In the example, thissensor 4 is sensitive to the infrared region, to be able to correctlysense the light emitted by the transmitter 1. The tube 2 is positionedbetween this latter and the sensor or receiver 4. This receiver can be,for example, a photodiode with a 1×5 mm sensitive area, model KOM2125produced by SIEMENS, or an optical sensor with 1×4.2 mm sensitive areaof the PSD (position sensor device) type, model S7105-05 produced byHAMAMATSU and also shown in the circuit schematic represented in FIG. 3;alternatively, the receiver 4 can be a CCD sensor of TSL 213 type,produced by Texas Instruments.

The transmitter 1 and receiver 4 are connected to a control unit 6,preferably of microprocessor type, arranged to evaluate signals, forexample electric (current) or digital signals I1 and I2 generated by thereceiver 4, which are fed to the unit 6 via outputs 8 and 9 of saidreceiver. On the basis of these signals and a predefined control andcomparison algorithm, the control unit 6 evaluates whether there isfluid 3 in the tube 2, whether it is moving and also its flow rate. Thepurpose of this is to determine whether the feed of the fluid 3, forexample to a mechanical member (not shown, for example a bearing asaforestated), is correct (for example for the purpose of lubrication).

The control unit 6 generates a reference signal K fed to an input 4 ofthe receiver 4.

In general, the light emitted by the transmitter 1 strikes the fluidfeed tube 2; this light is then deflected by the irregularities formedby the fluid flow through the tube, and strikes the receiver 4 able totransform the light signal into electrical signals which, sensed by theunit 6, enable this latter to provide an image or profile of the imageof the flow of the fluid 3 being monitored, which is hence related tothe image sensed by said receiver 4. This is achieved by the methoddescribed in relation to FIG. 3.

FIG. 1 shows the use of the invention to determine the movement of afluid within a tube or conduit, whereas FIG. 2 shows the use of theinvention to determine the presence of an atomized fluid or a fluiddefined by powder (suspended in another liquid or gaseous fluid).

In the figure under examination, in which parts corresponding to thoseof the already described figure are indicated by the same referencenumerals, the light radiation emitted by the transmitter 1 strikes aspray of atomized fluid or powder 13 emerging from a nozzle 14 and isreflected towards the receiver 4 positioned on that side of the fluid 13on which the transmitter 1 is also located. The light striking thislatter causes it to emit electrical signals which reach the unit 6 toenable this, in the aforedescribed manner, to sense the presence of thespray 13, its intensity and, if required, also its direction in space.The unit 6 then acts on the feed of fluid to the nozzle 14 or on asupport 15 for this latter, with which the nozzle is rigid, which canmove (with translatory and/or rotary movement) in space (by virtue of ausual electric motor, not shown) to modify the direction and/or flowrate of the spray.

This “reflection” method, which can also be used to monitor a flowwithin a tube, also enables flows of fluids consisting oflight-impermeable substances, such as paint, to be monitored.

The various components of the device of the invention are shown in FIG.3, where they are indicated by the same reference numerals whichidentify them in the preceding figures.

FIG. 3 shows the receiver 4 defined by an optical position sensor of thePSD type, used to intercept the direct (FIG. 1) or reflected (FIG. 2)image; this image is formed by modulating the infrared light emitted bythe transmitter 1 polarized by the polarization current frompolarization resistors 30 and 31. A gate 32 of the microprocessor unit 6is connected to the resistor 30 and is used to reduce the value of thecurrent circulating through the transmitter (diode) 1 when the device ofthe invention is in the stand-by condition to limit the electricityconsumed by the circuit and to prevent reduction of the average usefullife of the component (the transmitter).

The sensor 4 is struck by the light reflected by the fluid leaving thenozzle 14 (FIG. 2) or by the constricted light originating from thetransmitter of FIG. 1; in this second case, the sensor 4 senses the“shadow” of the flow of fluid which strikes it and on the basis of thisdefines the form and dimension of said fluid. The method of use of thetransmitter 1 and sensor 4 shown in FIG. 1 can obviously be applied toFIG. 2 and vice versa.

As the sensor 4 is struck by a light (infrared) which is a function ofthe image of the monitored flow, the sensor 1 generates at its outputterminals 8 and 9 (photodiode anodes) two currents I1 and I2 based onthe position in which the infrared light image (flow profile) strikesthe optical sensor 4. These currents I1 and I2 polarize respectiveresistors 33 and 34 and enable a potential difference to be generatedacross the resistors.

The electrical signals or currents I1 and I2 are processed by a twostage amplifier circuit 35 formed from operational amplifiers 36 and 37and relative polarization networks comprising resistors and capacitors38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, the reference signalof which is obtained from resistors 52 and 53 and a filtering capacitor54. The circuitry suitably connected as indicated in the electricalschematic enables a differential amplifier to be formed which is able toamplify the said potential differences present across the resistors 33and 34.

The circuit 35 amplifies the differential signal produced by the sensor4 and at the outputs 57 and 58 of the two stage amplifier enablessignals to be obtained which are amplified respectively 1000 and 100times the level of variation of the sensed image at the inputs of saidtwo stage differential amplifier, enabling a device with a doublecontrol scale to be formed.

Said amplified signals are fed to the gates 60 and 61 of the unit 6 andcan be converted in known manner from analog signals to digital signalsby a usual ADC unit integrated into the unit 6 (not shown). Saidconversion enables the previously amplified signals to be transformedinto numerical values, said numerical values being a function of theimage relative to the monitored flow; by means of a processing andcomparison algorithm, they are able to determine if the image variationhas level and frequency values which are equal to or greater than aprogrammed minimum reference value. If the image variation level andfrequency values are shown to be less than the programmed referencevalue for an irregularity time greater than a further programmable alarmtime, an alarm signal is generated by the unit 6 at an output gate 63.

By means of polarization resistors 70 and 71, the signal leaving thegate 63 activates an output transistor 75, to generate an alarm signalconnected to a connection member 76 of a connector 77.

There is connected to the connection member 76 a usual elementcontrolling a member (for example a bearing of a machine tool) at whichthe fluid 3 arrives, or controlling the feed of an article to a workstation where it is subjected to the spray 13. Alternatively, there issimply connected to the member 76 a warning alarm (acoustic orlight-emitting) for the textile machine or work station with which thepresent invention is connected.

The resistor 70, 71 and the transistor 75 form part of an alarm andprotection circuit 80 connected to the aforesaid member. This circuitcomprises a resistor 81 used as a shunt resistor which enables thecurrent provided by the transistor 75 to be measured, the voltage dropacross it being a function of the operated current, i.e. the currentrelative to the load which is to be piloted, for example a solenoidcontrol valve or more simply the stop relay of the machine tool; thiscontrol enables damage to the transistor 75 to be prevented in the caseof mistaken connection, for example a short circuit, or excessivecurrent absorption.

This voltage drop is measured by the unit 6 via a gate 82 connected tothe circuit 80 by a decoupling resistor 83, and provides protectionagainst any short-circuiting at the member 76; in this respect in thecase of extra current exceeding the defined maximum value, the unit 6deactivates the transistor 75 to protect the member 76.

A diode 84 also acts as protection against voltage reversal between thecollector and emitter of the transistor 75.

A circuit 88 displaying the correct operation of the flow feedmonitoring device is also connected to the unit 6. This display circuit88 comprises transmitters or LEDs 89 and 90 which are connected tooutput gates 91 and 92 of the unit 6 by polarization resistors 93 and94. These LEDs generate lights of different colours (for example greenand red) to indicate correct operation of said device.

The circuit 88 is also connected to a circuit 96 acting as the deviceresetting circuit. This circuit 96 comprises a photodiode 97 polarizedby a resistor 98 and piloted by the unit 6 via a gate 99 thereof. Thecircuit comprises a phototransistor receiver 100 and a polarizationresistor 101 which define an optical reflection key, the activationstate of which can be read by the unit 6 by an input reading at a gate103. This optical key can be used as the RESET key of the device of theinvention.

In addition to the other usual connection members, the connector 77comprises an input 106 enabling a programming/communication unit (notshown) to be connected to the device to enable the limiting imagevariation level parameters and relative alarm times to be programmed, onexceeding which the unit 6 generates a STOP signal via the member 76 andactivates the LED or alarm (for example red) 90.

Said communication takes place via the respective RX input and TX outputof the unit 6 interfaced at the connector 77 via an input decouplingresistor 107 and an output buffer 108 respectively. That circuit portioncomprising said buffer 108 and the resistor 107 is connected to outputsand inputs 110, 111 and 112 of the unit 6 (the RX input coinciding withthe input 100 and the TX output coinciding with the output 111) andrepresents a programming interface 113. By means of this, alarm timesand flow monitoring values can be programmed.

The circuit schematic of FIG. 3 also comprises a feed circuit 114 formedby known L-C low pass filters defined by an inductor 115 and capacitor116, a protection/feed polarity reversal diode 117, a first stabilizercircuit 118 and relative polarization components 119 and 120, and thefilter 121 the values of which predetermine the stabilized outputvoltage of the circuit 118 identified by VCC and fixed at 5 V.

A second feed stage of 3.3 V is formed by a second stabilizer circuit125 and relative antidisturbance filters consisting of capacitors 126and 127.

The circuit 114 is connected to a power reset circuit 130 comprising athird stabilizer circuit 131 connected to resistors 132 and 133, thislatter being connected to a gate 134 of the unit 6; this circuit enablescorrect data control and salvaging in case of network defects or holesor network voltage drops.

The circuit schematic also shows other members which have not beendescribed, but which define known parts having functions evident to theexpert of the art in the light of the aforegoing description and thecircuit schematic itself.

One embodiment of the invention has been described; others are howeverpossible in the light of the aforegoing description and are to beconsidered as falling within the present document.

1. A device for monitoring the flow of a fluid (3, 13) flowing throughor from a conduit (2), such as a lubricant or an article treatmentfluid, said fluid being a liquid, a gas or containing powder insuspension, said device comprising light-emitting means (1) arranged toirradiate a light radiation towards said flow of fluid (3, 13) andsensor means (4) for said radiation, characterised in that the sensormeans are image sensors arranged to sense the image projected onto themby the fluid (3, 13) struck by said light radiation, said image sensormeans (4) generating at least one output signal (I1, I2) depending onthe presence thereon of the sensed flow image, said signal representingin this manner characteristics of the fluid passing through the conduitor emerging from it such as its state of movement or rest, its flow rateor its direction in space.
 2. A device as claimed in claim 1,characterised in that the fluid being monitored is an atomized fluid(13).
 3. A device as claimed in claim 1, characterised in that the fluid(3) lies between the light-emitting means (1) and the sensor means (4).4. A device as claimed in claim 1, characterised in that the fluid (13)lies on one side of the light-emitting means (1) and of the sensor means(4), which themselves are located on the same side of the fluid (13). 5.A device as claimed in claim 1, characterised in that the sensor means(4) are a photosensitive element.
 6. A device as claimed in claim 1,characterised in that the sensor means (4) are an optical sensor.
 7. Adevice as claimed in claim 6, characterised in that the optical sensoris a PSD.
 8. A device as claimed in claim 6, characterised in that theoptical sensor is a CCD.
 9. A device as claimed in claim 1,characterised in that the sensor means (4) are connected tomicroprocessor evaluation and control means (6) to which the at leastone signal emitted by said sensor means is fed.
 10. A device as claimedin claim 1, characterised in that the sensor means emit two signals (I1I2) on the basis of the sensed fluid image.
 11. A device as claimed inclaim 1, characterised in that the signal emitted by the sensor means isan electrical signal.
 12. A device as claimed in claim 1, characterisedin that the signal emitted by the sensor means is a digital signal. 13.A device as claimed in claim 9, characterised in that the evaluation andcontrol means (6) are programmable via a programming interface (113) towhich these means are connected.
 14. A device as claimed in claim 9,characterised in that the evaluation and control means (6) are part ofan electrical circuit comprising a resetting circuit (96) and an alarmand protection circuit (80).
 15. A device as claimed in claim 14,characterised in that the alarm and protection circuit (80) is connectedto a connection member (76) for connecting the device to a memberreceiving the fluid being monitored.
 16. A method for monitoring theflow of a fluid (3, 13) flowing through or from a conduit (2), such as alubricant or an article treatment fluid, said method consisting ofgenerating a light radiation which is directed towards said fluid, andis then sensed after the fluid has interfered with it, characterised bycomprising: a) sensing the image of said fluid generated on image sensormeans (4) which are struck by the light radiation directed towards thefluid (3, 13); b) comparing the sensed image of the fluid withpredetermined values to identify characteristics of the fluid such asits state of movement, its state of rest, its flow rate, or itsdirection in space.
 17. A method as claimed in claim 16, characterisedin that the fluid image is sensed by reflection of the light radiationwhich strikes it.
 18. A method as claimed in claim 16, characterised inthat the fluid image is sensed indirectly via the shadow which itprojects onto the image sensor means (4).
 19. A method as claimed inclaim 16, characterised in that the fluid flow rate is regulated on thebasis of the sensed fluid characteristics.
 20. A method as claimed inclaim 16, characterised in that a member reached by the fluid beingmonitored is acted upon to regulate its operation on the basis of thecharacteristics of the sensed fluid.
 21. A method as claimed in claim20, characterised in that said regulating of the operation of the memberreached by the fluid being monitored also includes halting said member.22. A method as claimed in claim 20, characterised in that saidregulating of the operation of the member reached by the fluid beingmonitored includes regulating its spatial attitude.